A vast majority of biologically active molecules including growth factors, cytokines, neurotransmitters and hormones transduce signals via specific cell-surface receptors. Some of these receptors are then coupled to heterotrimeric GTP-binding proteins (G proteins) which, upon activation, relay signals to a variety of cellular effectors including at least four phospholipase C (PLC) variants and adenylyl cyclases.
G proteins mediate external signals by forming heterotrimers consisting of an alpha, beta and gamma subunit. Several isoforms of each subunit have been identified and therefore, through subunit heterogeneity, G proteins effectively integrate multiple signaling cascades. The alpha subunits of G proteins contain the GTP binding site and intrinsic catalytic GTPase activity. Based on sequence similarity and function, these subunits have been classified into four major groups; Gs, which stimulate adenylyl cyclases; Gi, which inhibit adenylyl cyclases; Gq, which activate PLC isoforms and G12/13, which mediate pathways associated with cell growth and differentiation (Hamm, J. Biol. Chem., 1998, 273, 669-672).
G-alpha-S1 (also known as Gs-alpha, short form) is one of four distinct members of the Gs subfamily of G proteins which result from alternate splicing of the pre-mRNA. G-alpha-S1 is the shortest of the Gs isoforms lacking a 15 amino acid insert and is expressed predominantly in the heart, liver neostriatum and platelets (Kozasa et al., Proc. Natl. Acad. Sci. U.S.A., 1988, 85, 2081-2085; Mattera et al., FEBS Lett., 1986, 206, 36-42).
Support for a unique functional activity of G-alpha-S1 comes from studies on .beta.-adrenergic receptors in S49 lymphoma cells in which Gs proteins were found to redistribute to distinct membrane compartments, G-alpha-S1 moving from light density membranes to the plasma membrane, upon isoproterenol treatment (Kvapil et al., Eur. J. Biochem., 1994, 226, 193-199). Overexpression of G-alpha-S1 in the hearts of transgenic mice resulted in a 2.8-fold increase in mRNA but an 88% increase in Gs activity suggesting that the membrane content of G-alpha-S1 is significantly altered (Gaudin et al., J. Clin. Invest., 1995, 95, 1676-1683). Other studies have shown that the concentrations of G-alpha-S1 change during developmental phases in the heart, kidney, liver, brain, myometrium and adipose tissue (Novotny and Svoboda, J. Mol. Endocrinol., 1998, 20, 163-173).
Currently, there are no known therapeutic agents which effectively inhibit the synthesis of G-alpha-S1.
Consequently, there remains a long felt need for additional agents capable of effectively inhibiting G-alpha-S1. Therefore, antisense oligonucleotides provide a promising new pharmaceutical tool for the effective and specific modulation of G-alpha-S1 expression.